Electric discharge device having a filling of gas or vapor



24, 1939. i Eg c 2,145,180

ELECTRIC DIS CHARGE DEVICE HAVING A FILLING OF GAS OR VAPOR Filed Jan. '7, 1936 INVENTOR Ernst Frieder'ich 3* 6.4%

' A TO RNEY Patented Jan. 24,. 1939 UNITED STATES ELECTRIC DISCHARGE DEVICE HAVING A FILLING F GAS 0R VAPOR Ernst Friederich, Berlin, Germany, assignor to General Electric Company, a corporation of New York Application January 7, 1936, Serial No. 58,001

Germany January 8, 1935 3 Claims. (01. 2 50-169) My invention relates to improvements in electric discharge devices having a filling of gas or vapor, and the object of the improvements is to provide a discharge device which is equipped 5 with means sensitive to light rays for throwing the same into and out of operation. With this object in view my invention consists in providing one or more photo-electric controlling electrodes within the device, which electrodes are adapted when impinged upon by light rays to emit electrons and thus to cause a current from the cathode to the anode.

Electric discharge devices of this type maybe used wherever it is desired to excite the device by light rays. For example in curves of street railways it may be desirable to excite lamps illumihating the curve only when a car passes through the curve, in which case the electric discharge device is ignited by light rays emanating from the head lights of the car.

As distinguished from systems in which the discharge devices are excitedby means of separate photo-electric tubes, in my improved device the photo-electric discharge from the said electrode or electrodes is intensified by the same filling of gas or vapor as the current flowing from the cathode to the anode, and the variation of the potential of the controlling electrode or electrodes is not only the result of the electron emission, but also that of ions produced in the receptacle, because the potential of the discharge device is suficient to cause ionization. Further, the current of electrons and ions flowing between the photo-electrically sensitive electrode and the anode takes part in the priming of the discharge between the cathode and the anode. By reason of the negative characteristic of the gas discharge the intensity of the anode current rises, immediately after ignition, up to a value limited by the outer resistance. Therefore the photoelectric effect needed for exciting a strong anode current is exceedingly small.

For the purpose of explaining the invention several examples embodying the same havebeen shown in the accompanying drawing in which the same reference characters have been used in all the views to indicate corresponding parts. In said drawing,

Fig. 1 is a diagrammatical view partly in section showing an electrical discharge device and the circuits thereof, and

Figs. 2 to 6 are similar views showing modifications.

In the construction shown in Fig.1 the cathode 1 and the anode 8 of an electric lamp l are conanode,

cuit 21, 28 includes a resistance 9 by means of 1 which the anode current is limited.

The upper and lower halves of the transformer secondary winding acting additively serve to impress between the grids 3, 4, and the anode, a potential which is considerably higher than that applied between the cathode and anode by the upper half of the transformer winding alone. Consequently, when light impinges on these grids the photo-electrons thus produced acquire a sufficient velocity in the'direction of the anode to initiate an ionizing discharge.

Though the potential difference of the tube falls off immediately after ignition so far that the velocity of the ions produced by the discharge is not very high, it may be desirable in some cases to dispose the photoelectric layer outside the path of the discharge between cathode and For this purpose the controlling electrode may be made in the form of an open or closed ring located around the said path, as is shown in Fig. 2. In this figure the annular photoelectrically sensitive electrode has received the reference character It). The voltage is applied. to the said electrode through a capacity-comprising outer plates II and I2, the inner plate being provided by the ring [0. When the capacity coupling of the parts I0 and II and I2 is variable the variable capacity 5 may be dispensed with. The cathode I3 is directly heated.

The other parts of the device are similar to those described with reference to Fig.1, and the same letters of reference have been used to indicate corresponding parts.

The operation of the device is the same as has been described with reference to Fig. 1. But the discharge from the cathode passes through the annular grid Ill without acting on the photoelectric coating thereof.

When the voltage of the anode is high the area of the ring I0 is preferably screened by a grid or net which is not coated with photoelectric material, in order to reduce the attractive power of the anode and to prevent ignition while the electrode is not impinged upon by light rays. In the construction shown in Fig. 3 the lamp l comprises an annular electrode [4 having a photoelectrically sensitive coating, and the: said electrode is provided with a screen having no such coating.

In Fig. 4 I have shown another modification in which additional means are provided for protecting the photoelectrically sensitive layer, which means consist of an electromagnetic coil I! placed around the tube l and adapted to produce a magnetic field in the direction of the said tube. As shown the said coil is placed around the portion of the tube in which the electrode I4 is located. But I wish it to be understoodv that my invention is not limited to this feature and that the coil may extend the whole length of the tube. As is known to those skilled in the art the magnetic field has the function to compress the discharge from the cathode around the axis of the tube after ignition, so that the said discharge is held away from the sensitive layer of the electrode I4. The coil I1 is energized by the anode current, the lead 40 connecting the anode with the secondary 26 of the transformer including the said electro-magnetic coil.

In order to produce a high photoelectrical effeet the controlling electrode may be suitably shaped so that many light rays impinge thereon. In Fig. 5 I have shown a construction in which the light rays are assumed to pass into the tube in axial direction, as is indicated by the arrows l9, and in order to increase the effect of the light rays on the electrode 20, the said electrode and the sensitive layer thereof are made in the form of a conical funnel 2D.

In the construction shown in Fig. 5 the receptacle 29 has a large cross-sectional area, as may be desirable in some cases, and in order to compress the discharge around the axis of the tube, for example in order to have a higher intensity, the tube is surrounded all over its length by an electro-magnetic coil 2! the energization of which preferably depends on. the fiow of the anode current. It is not desirable to have a coil of many windings, because thereby the light given oil by the device would be reduced. Therefore the circuit 33 of the coil. 2| is notdirectly connected with the anode circuit 3|, but it includes the secondary 32 of a transformer l8. the primary 33 of which is included in the anode circuit 31, the number of the windings 32 being small as compared. to that of the coil 33, so

that a current of low voltage and high intensity is, induced in thesecondary 32.

In the examples so far described the grids 3, 4, ll], I4 and 20 are energized. by alternating current. But I wish it to be understood that my invention is not limited to thisfeature and that any other appropriate voltage. may be applied to the said grids, for example direct current or a variable voltage controlled by a suitable device. Where direct current is used suitable means are provided for disconnecting the grid from the exciting voltage, the said means being preferably constructed so that the current is interrupted at least within periods of twenty seconds. Fig. 6 shows an example of a suitable device. The lighting tube is similar in construction to the one illustrated in Fig. 3. Butit is connected to a supply of difierent current. The lead 35 connecting the anode 8 with the positive terminal of the supply of direct our- I rent includes the aforesaid resistance 9, and

also a capacity 36. A small gas discharge tube 38 is connected in shunt to the capacity 36 by means of leads 31. The construction of such devices for interrupting currents is known in the art and therefore I deem it not necessary to describe the same more in detail.

When an alternating voltage is applied to the grid it is preferred'to impart thereto a lead of a little more than 180 relatively to the voltage of the anode, so that a very slight positive displacement of the voltage of the grid is sufficient in order to have the voltage of the grid still positive during. the positive half-wave of the voltage of the anode.

It is dii'licult to screen the photoelectrically sensitive. layer relatively to the radiation of the cathode Without simultaneously influencing the discharge, and therefore I prefer to use a photoelectrically sensitive material which does not respond to light radiated by the heated cathode. Suitable materials are tin, potassium and zinc.

I claim:-

1. An electron discharge device comprising an envelope containing an electron-emitting cathode, an anode and an ionizable material, means for-controlling the initiation of an ionization discharge between the cathode and anode, said means comprising a plurality of members, one of which is light-sensitive and is removed from the discharge path, and another of which is insensitive to light and is positioned within the discharge path.

2. A lamp comprising an envelope containing a thermionic cathode, an anode and an inert gas, means for initiating an ionization discharge through said gas, said means comprising a metal 'member interposed between the cathode and anode and adapted to be charged, said member having a portion sensitive to light and positioned within the discharge path except for said portion.

3. An electron discharge device comprising, an envelope containing a thermionic cathode, an anode and an inert gas, means for initiating an ionization discharge through said gas,said means comprising a ring coated with light-sensitive material and surrounding the discharge path, and an apertured diaphragm. secured to said ring, across the opening thereof and positioned within the discharge path.

ERNST FRIEDERICH.

CERTIFICATE OF CORRECTION.

Patent No, 2,1h5,l80.' January Zh, 1959.

ERNST FRIEDERICH It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 1, second column, line 21, after the word and period "discharge." insert the following sentence:

when illumination of the grids 5, L and electron discharge from the said grids cease, the electron discharge from the cathode 7 is interrupted when a negative impulse is imparted by the transformer to the anode 8.

page 2, second column, lines 1+5 and 55, claims 2 and '5 respectively, for "ionization" read ionizing; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office Signed and sealed this ll th day of March, AqD. 19590 Henry Van Arsdals.

- (Seal) Acting Commissioner of Patents.,. 

